Instant water dispensers for supplying hot or cold water on demand without delay are of great benefit to consumers. Hot water can be instantly delivered for the preparation of coffee or tea and cold water may be immediately provided on a hot day without having to stock beverages in the refrigerator.
The use of an instant water dispenser on the Sabbath has limitations. According to the Jewish religion, it is forbidden to initiate the flow of electricity or to heat water on the Sabbath to a near to scalding temperature; however, the flow of electricity may be initiated prior to the onset of the Sabbath such as by means of a timer. Thus a consumer is forbidden to cause hot water to be dispensed on the Sabbath from such a water dispenser because unheated water would be introduced to the heating chamber in response to the dispensing operation and then be heated by a heating element to the near scalding temperature.
U.S. Pat. No. 7,672,576 discloses a water dispenser with a Sabbath function. During a daily mode, a water valve controls the flow of water from an inlet to a hot water reservoir to refill the hot reservoir whenever the water level falls below a prescribed level. During a Sabbath mode, a controller turns off the valve, preventing water flow into the hot reservoir while the water remaining in the hot reservoir is constantly heated at a less than boiling temperature.
US 2009/0103907 discloses a water dispenser with similar functionality, and further describes a safety device for switching off, and preventing the overheating of, the heating elements from when the water level is low.
Since unheated water is prevented from being admitted into the hot water reservoir during the Sabbath mode, the remaining water is liable to evaporate to cause the water level to drop below a predetermined low level. After the heating elements of these as well as other prior art water dispensers are automatically deactivated when the water level in the hot water reservoir falls below the predetermined low level, the remaining water within the hot water reservoir becomes cooled and naturally cannot be reheated during the Sabbath.
It is an object of the present invention to provide a hot water dispenser that is permissible to operate during the Jewish Sabbath and that prevents the heating elements from overheating when a low water level condition is detected without being deactivated.
Other objects and advantages of the invention will become apparent as the description proceeds.